INVESTIGADORES
OLIVERA Maria Eugenia
congresos y reuniones científicas
Título:
1H-driven 19F spin diffusion and cross polarization measurements for distance and structure determination in ciprofloxacin derivatives
Autor/es:
GARRO LINCK Y SPIESS HW; CHATTAH AK; ROMAÑUK CB; OLIVERA ME; MANZO RH; GRAF R; MONTI GA; SPIESS HW
Lugar:
Gotemburgo, Suecia
Reunión:
Congreso; EUROMAR 2009; 2009
Resumen:
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Dipolar-driven
spin diffusion in solid state Nuclear Magnetic Resonance (NMR) is a robust
approach for obtaining homonuclear distances. In this work, we applied the
centerband-only detection of exchange (CODEX) technique [Wenbin Luo and Mei
Hong. J. Am. Chem. Soc. 2006,
128, 7242-7251] on a new pharmaceutical compound, ciprofloxacin saccharinate [Romañuk
et al. J. Pharm. Sci. DOI: 10.1002/jps.2168]. This compound exhibits polymorphism, and
presents well distinguished solid forms, CIP-SAC (I) and CIP-SAC (II). In
particular, CIP-SAC (II) can be obtained as a monocrystal.
To
carry out the analysis, we use crystallographic data obtained from single
crystal X-ray diffraction of CIP-SAC (II), as a starting point to perform the
fittings of CODEX data. We calculate the value of Fij(0), the overlap integral describing the probability
that single-quantum transitions occur at the same frequency for spins i and
j, for CIP-SAC (II). Then, considering this value, we were able to determine
distances and molecules per unit cell in CIP-SAC (I).
Diffraction
data show that CIP-SAC (II) presents two molecules per unit cell (one in the asymmetric
unit) with different orientations. From 13C NMR data, CIP-SAC (I) shows at least
two molecules per asymmetric unit.
Results
from CODEX, in addition to 19F
spectra, T1F and 13C CP-MAS (cross polarization and
magic angle spinning) experiments performed on both solid forms of CIP-SAC, give us evidence that CIP-SAC (I) is a mixture
of two polymorphs, one of them probably CIP-SAC (II).
We
complemented these experiments with 1H-19F CP-MAS experiments
with variable contact time.
